Tips for keeping plants alive outdoors in winter

I don’t like to get up early on Saturday mornings, but I was happy that I was out and about last Saturday morning, when many of Wichita’s lawns were covered with their first frost of the season, and the evergreens, when the sun shone through the frosty boughs, looked bejeweled.

I don’t like to get up early on Saturday mornings, but I was happy that I was out and about last Saturday morning, when many of Wichita’s lawns were covered with their first frost of the season, and the evergreens, when the sun shone through the frosty boughs, looked bejeweled.

It all seems too early, but kind of expected, too.

The seasons are clashing at Botanica, where you can still stick your nose in a sun-warmed cup of rose petals, and you can still inhale the smell of summer in the wildflower meadow. But the Christmas lights for Illuminations are going up, and the frost has nabbed some of the tropical plants.

At home, overnight the coleus shrubs that provided such height to the front porch were gone (the volunteers that rooted themselves in the soil are still looking fine). I’m scrambling for some alternatives to fill the holes.

One new addition is an evergreen, a Baby Blue false cypress, which needs a new pot and attentive watering. That can be a challenge in the winter. But I always want potted evergreens on the front porch, and, if successful, this will extend the season beyond the cut Christmas trees that I usually rely on as stand-ins.

Extension agent Bob Neier said that evergreens in pots should be watered occasionally when the ground is not frozen. “If they’re in heavy concrete containers they’re going to be fine. Terracotta pots are going to crack,” he said.

I usually leave some other perennials and annual grasses in pots over the winter, too. Coral bells, for example, survive very well, and the grasses’ seedheads can stick around if they look good, even if the grasses themselves don’t come back.

Colorado State University has some helpful information on the Internet about ways to overwinter pots. I like to leave mine out to provide a decorative element. But if you just want to keep plants alive outdoors, here’s Colorado State’s advice:

“Cluster containers together in a protected site under the house eaves on the north or east side. Place larger pots to the outside and smaller pots to the inside of the cluster. Water pots well, then mulch heavily with straw, leaves, hay or shredded bark. Provide a thick layer of mulch or bales of hay around the outer edge of the cluster. Also, mulch over the top of the pots to lessen the impact of root-killing temperature fluctuations. Check every two weeks and water as necessary.”

For evergreens, I’ve read that they should be hardy to temperatures at least two zones colder than where you are. In my case, the Baby Blue is a Zone 4 plant, two zones colder than our Zone 6, so that should cover it.

“Success in overwintering evergreens in containers hinges on a number of factors, some of which you may have little control over,” Colorado State says. “First, the plant needs to be sufficiently cold hardy to withstand root temperatures which will be colder than those encountered by a plant growing in the ground. Be sure and select evergreens that are winter hardy well north of where you are growing them.

“Secondly, plants in larger pots and containers are usually more successful in overwintering than plants in small containers. Fluctuations in freezing and thawing can lead to root damage and death. This can be more pronounced in smaller pots. One way to overwinter smaller containers is to sink them in the ground or mulch up to their rims. This will help reduce soil temperature fluctuations. It may be impractical to bury large containers due to their size and weight.

“Thirdly, maintaining the correct moisture levels in the soil over winter is critical. If the container dries out, the plant will desiccate and die. Or, conversely, if the soil stays too wet the roots will rot. Maintaining the proper moisture level is important but can be difficult during warm moist periods in winter.

“Lastly, evergreens should receive some sun during the winter. Most, except the most hardy, should not be overwintered in full sun but rather where they receive some shade. This location will help reduce moisture evaporation and help protect the soil in the container from going through wide temperature fluctuations due to warming by the sun and nighttime freezing.”

I think it will be a challenge, but it’s time to try. I’d like to add a light-green foliage to contrast with Baby Blue – and the inevitable little cut Christmas tree.